JP6931739B2 - A method for manufacturing a spark plug electrode and such a spark plug electrode, and a spark plug provided with the spark plug electrode. - Google Patents

Description

The present invention relates to the spark plug electrode according to claim 1, a spark plug including the spark plug electrode according to claim 6, and a method for manufacturing the spark plug electrode according to claim 7.

The life of a spark plug is limited because of the durability of the part. One such component is a spark plug electrode or a material that is a raw material for manufacturing a spark plug electrode. While the spark plug electrode is used in an internal combustion engine, the spark plug electrode and its material are constantly exposed to corrosion and erosion processes. Oxidation of the spark plug electrode material and ignition spark plasma during the operation of the internal combustion engine causes the ignition gap between the spark plug electrodes to increase over time, thus causing the spark plug to lose its ignition capability and need to be replaced. It becomes.

Correspondingly, the purpose of today's research is to find materials and material combinations that have high corrosion and erosion resistance. Spark plug electrodes made of nickel alloy currently used have a life of about 30,000 km to 60,000 km. Spark plug electrodes made of precious metal alloys have a lifespan of 60,000 km to 90,000 km, but are clearly more expensive than spark plug electrodes made of nickel alloy due to material costs.

In order to reduce material costs, nickel alloy electrode bodies are often combined with precious metals or precious metal alloy ignition elements. The electrode body and the ignition element are bonded to each other by material bonding using a welding method. Frequently used precious metals are platinum and iridium and alloys containing these elements.

However, since precious metal alloys and nickel alloys have different coefficients of thermal expansion, mechanical stress is generated in the welded joint. In extreme cases, the welded joint breaks and the precious metal-based ignition element separates from the electrode body, making the spark plug unusable. This problem is more apparent in the case of the ignition element made of Ir as the raw material than in the case of the ignition element made of Pt as the raw material. This is because the coefficient of thermal expansion differs between the Ir alloy and the Ni alloy by a coefficient of 2.

There are various welding methods that seek to produce a stable welded joint between the ignition element and the electrode body. Laser welding is extremely widely used when coupling an ignition element made of Ir as a raw material and an electrode body made of Ni as a raw material. For example, from Patent Document 1, in the laser welding method, the CW laser beam is statically directed to the coupling region between the ignition element and the electrode body, the spark plug electrode is around the longitudinal axis thereof, or the laser beam is the spark plug electrode. Those that rotate around are known. A similar method is known from Patent Document 2, but here, the pulsed laser beam is statically directed to the coupling region. In Patent Document 3, two welded joints that are slightly offset from each other are generated by a static laser beam.

In spark plugs available today, precious metal-containing ignition elements and electrode bodies are usually welded using one of the two methods described at the beginning, and have the problems described above.

German Patent Application Publication No. 10103045 European Patent Application Publication No. 0671793 German Patent Application Publication No. 201410223792

An object of the present invention is to provide a spark plug electrode, a spark plug electrode having the longest possible life of the spark plug, and a method for manufacturing the electrode, alleviating the problems described above.

The subject of the present invention is a spark plug of the present invention comprising an electrode body made of a first material, which is bonded to each other by a material bond via a welded joint, and an ignition element forming an ignition surface of the spark plug made of the second material. The electrode solves the problem by making the mixture D of the first material or the second material less than 15% by weight in the half of the welded joint adjacent to the ignition element.

In order to calculate the mixing degree D, a line scan is performed in the welded joint to calculate the elemental concentration along these lines. Normally, the scanning lines are evenly spaced from each other and extend perpendicular to the longitudinal axis of the ignition element, i.e. parallel to the weld joint. Preferably, a line scan is performed on the ignition element to determine a reference value for the elemental concentrations of the first and second materials. Preferably, another line scan is performed at the interface between the ignition element and the weld joint. In addition, yet another line scan of any number can be performed on the welded joint. Advantageously, a minimum of 4 line scans is the basis for determining the degree of mixing. In each next line scan, the numerical value of the element concentration in each line is obtained for the first material and the second material. For example, in an alloy, it is sufficient to calculate only the concentration of the principal component and use it for another evaluation to determine the mixing degree D. From the elemental concentration determined for each line, the mean and standard deviation for each material or element are calculated. Next, the standard deviation is the mixing degree D, which is a measure of the distribution of elements in the welded joint and each material. The smaller the mixing degree D, the more uniform the distribution of elements in the welded joint. According to the applicant's investigation, the more uniform the distribution of elements, the smaller the difference in the coefficient of thermal expansion between the ignition element, the welded joint, and the electrode body, and the mechanical stress at the interface decreases accordingly. It became clear. Thus, the possibility of crack formation in the welded joint is reduced and the life of the spark plug is extended. In this way, the mixing degree D also becomes a characteristic that affects the quality of the welded joint and the weld.

In an example involving four line scans (n = 4), the degree of mixing is calculated as follows.

Here, the average value is as follows.

In order to determine the reference value of the element concentration of the first material and / or the second material, the first line-scan L ₁ is performed outside of the welded joint on the igniter element.

Uniform distribution does not have to mean that the first material is mixed with the second material in the weld joint to form a new alloy. From the applicant's search, to obtain a stable and long-life welded joint, from approximately the first material and / or from the approximately second material and / or a mixture of the approximately first and second materials. It has become clear that there is a complete advantage even when the region composed of is present in the welded joint. When line-scanning the entire of these various regions, the material or elemental concentrations are averaged over these regions. The degree of mixing D then indicates how uniformly these different regions are distributed within the welded joint.

Another result of the applicant's investigation is that in the prior art spark plug electrodes, inconvenient cracks adjacent to the ignition elements are formed primarily in half of the welded joint. Thus, in order to determine the quality of the welded joint, it is sufficient to calculate the mixing degree D of half of the welded joint directed toward the ignition element.

Of course, by increasing the number of line scans, the size of the area to be investigated in the weld joint and / or the number of elements and materials to be investigated, the uncertainty in the measurement of the degree of mixing D is reduced, and at the same time, the mixture is mixed. It is possible to increase the effectiveness of degree D. The dependent claims relate to advantageous modifications of the invention in which the modifications listed above have been partially implemented.

The applicant's search revealed that it would be more advantageous if the mixing degree D was 12% by weight or less. For the first material or the second material in the half of the welded joint adjacent to the ignition element, the spark plug electrode with a mixture D of 10% by weight or less gave particularly satisfactory results.

Alternatively, a mixing degree D of the first and second materials of less than 15% by weight, particularly 12% by weight or less, particularly preferably 10% by weight or less, is also advantageous. In this way, in the welded joint, the most uniform distribution of the two materials is established.

Preferably, the first material for the electrode body is a nickel alloy containing nickel or Ni as the main component or the largest single component. In order to satisfy the condition for the mixing degree D, it is sufficient that the Ni portion in the first material keeps the limit of the mixing degree D. The first material using Ni as a raw material has an advantage that it can be easily processed and the material cost is reduced.

In addition to or alternative to this, the second material of the ignition element is a noble metal or a noble metal alloy, in particular the noble metal is at least in the group Ir, Pt, Pd, Rh, Ru, Re, Os, Au, Ag. It is desirable that it is one element and is the main component or the largest single component in the alloy. In order to satisfy the condition for the mixing degree D, it is sufficient that the precious metal portion in the second material keeps the limit of the mixing degree D. The second material made from a noble metal has an advantage that the ignition element composed of the noble metal has high corrosion resistance and erosion resistance.

Another aspect of the invention relates to a spark plug having at least one spark plug electrode of the invention. Preferably, the spark plug electrode is formed as a center electrode.

A third aspect of the present invention relates to a spark plug electrode, particularly a method for manufacturing a spark plug electrode of the present invention. The manufacturing method includes the following steps.
・ Prepare the electrode body and ignition element,
・ Perform the welding process of forming a welded joint and connecting the electrode body and the ignition element.
-The welding beam is directed to the joint between the electrode body and the ignition element via the reflecting means, and a welded joint is generated.
-By tilting the reflective means, the weld beam is guided over the surface of the spark electrode to create a welded joint.

By tilting the reflecting means, especially periodically, a location-by-location modulation of the weld beam can be obtained on the surface of the spark plug electrode. The welding pool generated at the joint between the ignition element and the electrode body and on the joint surface gains further vitality by such site-by-location modulation, and this vitality is promoted by thermodynamics to make the first material the second material. Causes further mixing to mix with the material. By using such a welding method, the melted first material or the second material obtains a significantly longer reach, and further moves in the melting bath, which is the starting point at which the welded joint is generated, and is partially different. Can be mixed with material.

The reflecting means is, for example, a mirror or a so-called scanner.

Preferably, the weld beam is guided over the surface of the spark electrode along a line parallel to the longitudinal axis X of the ignition element. Advantageously, this longitudinal axis extends through the coupling surface between the ignition element and the electrode body, i.e. through the later welded joint.

It has become clear that the reflecting means is advantageous when it is tilted at a frequency of at least 1000 Hz. For example, the reflecting means is tilted at a frequency of 1200 Hz. In this way, the weld beam performs a movement substantially parallel to the longitudinal axis X of the ignition element and slides over the same line or region multiple times.

This is also supported, for example, by the condition that the spark plug electrode rotates during the welding process and the rotation frequency of the spark plug electrode is lower than the frequency at which the reflecting means is tilted. The tilting of the reflective means relatively quickly compared to the rotation of the spark plug electrode causes the weld beam to perform a scanner-like operation on the surface of the spark plug electrode.

For example, the weld beam can be, in particular, a laser beam emitted from a CW laser, such as a disc laser or a fiber laser. When combined with a scanner as a reflecting means, a laser scanner welding method can be obtained for the welding process.

The various embodiments described above the manufacturing methods of the present invention result in a welded joint resulting in a mixture D of less than 15% by weight for the first and / or second material. .. Thus, here, the advantageous effects described above in the case of the spark plug electrode of the present invention are brought about.

The figure which shows the example of the manufacturing method of the spark plug electrode of this invention. The figure of EDX measurement in the spark plug electrode of this invention and the two spark plug electrodes of the prior art. The figure of EDX measurement in the spark plug electrode of this invention and the two spark plug electrodes of the prior art. The figure of EDX measurement in the spark plug electrode of this invention and the two spark plug electrodes of the prior art. The figure which shows the example of the calculation of the mixing degree D. The figure which shows the mixing degree D of two elements of each of two samples produced by the known welding method in comparison with the sample of this invention.

FIG. 1 schematically shows an example of the production method of the present invention. What is shown is a spark plug electrode 1 including an electrode body 2, an ignition element 3, and a welded joint 4 that connects the electrode body 2 and the ignition element 3 to each other by material bonding. The ignition element 3 has a coupling surface between the electrode body 2 and the ignition element 3, or a longitudinal axis X extending perpendicularly to the welded joint 4 after the welding process. For example, the ignition element is formed in the shape of a rod or pin. The spark plug electrode 1 has a surface 7 formed by the surface of the ignition element 2 and the surface of the electrode body 2. The area on the surface of the spark electrode around the coupling surface between the electrode body 2 and the ignition element 3 is called a coupling portion. In the welding process, a melting bath and then a welded joint 4 are first generated at the joint surface and the joint portion.

A welding beam 5, such as a laser beam, is guided to a coupling portion between the electrode body 2 and the ignition element 3 through a reflecting means 6, for example, a mirror, where a welded joint 4 is generated. Therefore, the welding method is, for example, a laser scanner welding method in which a laser beam is directed to an object to be welded via a scanner to produce a welded joint. By moving the scanner, the laser beam is guided to a desired position on the object. Usually, a CW laser such as a fiber laser or a disk laser is used to generate a laser beam.

Normally, in the spark plug electrode 1, the melting bath for the welded joint 4 extends at least to the longitudinal axis X of the ignition element 3. Therefore, after the spark electrode 1 rotates around the longitudinal axis X in the welding process, the electrode body The coupling surface between 2 and the ignition element 3 is completely melted, that is, the welded joint 4 extends over the entire diameter of the ignition element 3.

Since the reflecting means 6 is periodically tilted while the welding beam 5 is incident on the surface 7 of the spark electrode 1, the welding beam 5 is executed by periodic movement along the surface 7. Preferably, the movement is parallel to the longitudinal axis X of the ignition element 3. By locally modulating the incident of the weld beam 5 in this way, the first material and the second in the welded joint 4 have significantly higher vitality in the molten bath at the coupling surface between the ignition element 3 and the electrode body 2. A more convincing mix with the material of is achieved.

Normally, the reflecting means 5 is inclined at a minimum frequency of 1000 Hz, here at a frequency of 1200 Hz. The rotation of the spark electrode 1 around the longitudinal axis X of the ignition element 3 has a much lower frequency.

In FIGS. 2a) to 2c), EDX diagrams of the cut surfaces of the three spark electrodes 1 manufactured by different welding methods are shown. In sample 1 (P1) of FIG. 2a), the welded joint was generated by a CW laser beam statically incident on the joint, and the spark plug electrode 1 was rotating around its longitudinal axis. The ignition element is composed of iridium. The electrode body is made of Ni alloy. Sample 2 (P2) of FIG. 2b) is a spark plug electrode 1 including an electrode body 2 made of Ni as a raw material and an ignition element 3 made of an Ir alloy. In sample 2, the welded joint is generated using a pulsed laser. Sample 3 of FIG. 2c) shows the spark plug electrode 1 of the present invention manufactured by using the manufacturing method of the present invention. The CW laser beam 5 is guided to the spark plug electrode surface 7 via the scanner 6. The ignition element 3 is made of Ir alloy, and the electrode body is made of Ni alloy.

The gray gradation on the cut surface reproduces different elemental concentrations. The welded joint of Sample 1 appears to have a perfectly uniform shade of gray. In contrast, the welded joint of Sample 2 forms a strongly wound vortex with different grayscales. In sample 3, welded joints show large and small regions with different grayscales that stand out relatively clearly from each other.

A mixing degree D for each sample is calculated to determine the quality of the welded joint. In order to determine the mixing degree D, the width y of the welded joint along the extension of the longitudinal axis X of the ignition element 3 is first determined. Along the four lines perpendicular to the longitudinal axis X of the ignition element 3, the element concentrations of the two main elements of the electrode body 2 and the ignition element 3, here Ni and Ir, are determined. One line (L4) is measured at the y / 2 position at the center of the welded joint, measured from the edge (upper edge) of the welded joint adjacent to the ignition element. The second line (L2) is measured at the upper edge of the welded joint. The third line (L3) is measured along half the distance between line 4 and line 3. The last line (L1) is measured at the ignition element 3 as a reference and all lines 1-4 have the same spacing with respect to each other. The wire covers 90% of the diameter of the welded joint, or, if this diameter is not constant, the diameter of the welded joint at the upper edge. The midpoint of the line is located on the extension of the longitudinal axis X of the ignition element 3. The elemental concentrations along the line are measured using EDX analysis (energy dispersive X-ray spectroscopic analysis), depending on the region as a whole, which may have different concentrations, for example in the case of Samples 2 and 3. You can see the average. In FIG. 3a), the arrangement of the lines L1, L2, L3 and L4 is shown by taking the sample P3 of the present invention as an example.

In Table 1, for the elements Ni and Ir, respectively, the element concentrations were recorded for 3 samples and 4 lines each. In the sample, the body is mainly composed of Ni and the ignition element is mainly composed of Ir. The rest of the proportions in some samples consisted of Rh and other elements, which were not considered in the analysis of welded joints.

In each sample, average values were formed for each element across the four lines. The degree of mixing D corresponds to the standard deviation of the mean for each element. The smaller the mixing degree D, the smaller the standard deviation. On average, this corresponds to a relatively uniform elemental distribution in the welded joint.

In an example involving four line scans (n = 4), the degree of mixing is calculated as follows.

Here, the average value is as follows.

In order to determine the reference value of the element concentration of the first material (nickel) and the second material (iridium), the first line-scan L ₁ is performed outside of the welded joint on the igniter element.

In FIG. 3b), two mixing degrees D are graphed for Ni and Ir in each sample. The two prior art samples 1 and 2 have a minimum mixing of 15% by weight for the two elements. Applicant's investigation revealed that the lower the mix, the more stable the welded joint. For Sample 3 of the present invention, the mixing of these elements is less than 10% by weight.

In connection with the applicant's investigation, EDX line scans were performed evenly spaced over the width y of the weld joint, from which the mean and standard deviation for the elements corresponded to the behavior described above. Alternatively, a study was also conducted to determine the degree of mixing D. The results for the degree of mixing D calculated over the entire width were not significantly different from the degree of mixing D calculated over half the width. Furthermore, the investigation revealed that in the case of the prior art spark electrode, cracks and breaks in the welded joint occur in the upper half of the welded joint, that is, in the half of the welded joint directed at the ignition element. Therefore, quality control or improvement of the upper half of the welded joint essentially contributes to the improvement of the durability of the spark plug. Focus on the upper half of the weld joint in determining the mix to improve the efficiency of quality analysis and quality control.

1 Spark plug electrode 2 Electrode body 3 Ignition element 4 Welded joint 5 Welded beam 6 Reflecting means 7 Surface D Mixing X Longitudinal axis

Claims (11)

-The electrode body (2) made of the first material and
An ignition element (3) made of a second material is provided, and the ignition element (3) is configured to form an ignition surface of a spark plug, and the electrode body (2) and the ignition element (3). In the spark plug electrode (1), which is bonded to each other by material bonding via a welded joint (4), the first material is a nickel alloy and the second material is an iridium alloy. A spark characterized in that the mixing degree (D) of the first material and the second material is less than 15% by weight in the half region of the welded joint (4) on the ignition element (3) side. Plug electrode. Spark plug electrode according to claim 1, wherein the degree of mixing (D) is characterized by comprising a 12 wt% or less (1). The spark plug electrode (1) according to claim 1, wherein the mixing degree (D) is 10% by weight or less. Before SL spark plug electrode (1) is the center electrode, the spark plug comprising at least one spark plug electrode according to any one of claims 1 to 3 (1). The first manufacturing method of the material made of the electrode body (2) and the second material made of the ignition element (3) and spark plug electrode according to any one of up to 3 from請Motomeko 1 Ru provided with (1) In
-Prepare the electrode body (2) and the ignition element (3),
A welding step of forming a welded joint (4) and connecting the electrode body (2) and the ignition element ( 3) is executed.
The welding beam (5) is directed to the joint portion between the electrode body (2) and the ignition element (3) via the reflecting means (6), and the welded joint (4) is generated.
A step in which the welding beam (5) is guided on the surface (7) of the spark plug electrode (1) in order to generate the welded joint (4) by inclining the reflecting means (6). How to include. The welding beam (5) is according to claim 5, characterized in that the surface (7) above, is guided said ignition element along one line which is parallel to the longitudinal axis (X) of (3) The method described. The method according to claim 5 or 6, wherein the reflecting means (6) is inclined at a frequency of at least 1000 Hz. 7. The seventh aspect of claim 7, wherein the spark plug electrode (1) rotates during the welding method, and the rotation frequency of the spark plug electrode (1) is smaller than the frequency at which the reflecting means (6) is tilted. the method of. Before Symbol welded joint (4), in the half area of the ignition element (3) side, for the first material及beauty before Symbol second material, it mixing degree (D) is less than 15 wt% The method according to any one of claims 5 to 8 , characterized in that. The method according to any one of claims 5 to 9 , wherein the welding beam (5) is a laser beam. Welding process is a laser scanner welding method, the method of any one of claims 5 to 10, characterized in that before Symbol reflecting means (6) is a scanner.

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